Chaotic mixing of shear-thinning fluids

Journal Article · Tue Nov 01 04:00:00 EST 1994 · AIChE Journal (American Institute of Chemical Engineers); (United States)

DOI:https://doi.org/10.1002/aic.690401103· OSTI ID:6658352

Niederkorn, T C; Ottino, J M ^[1]

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1. Northwestern Univ., Evanston, IL (United States). Dept. of Chemical Engineering

This article investigates the effect of shear-thinning viscosity on chaotic mixing when the kinematics first begin to deviate from Newtonian flow. Computations are done for a 2-D, time-periodic flow between eccentric cylinders. The effectiveness of mixing is analyzed by examining the asymptotic coverage of a passive tracer, character and location of periodic points, and the rate of stretching of fluid elements. Small variations in the velocity field associated with non-Newtonian kinematics produce large effects in the chaotic advection of a passive tracer. The stretching rate remains exponential, but with a long time constant as the shear-thinning effect increases, often resulting in the birth of new periodic islands and a decrease in the asymptotic coverage of the tracer. Exceptions to these observations are possible: both the stretching rate and the asymptotic coverage might increase as shear thinning increases. Results also indicate that suitable manipulation of operating conditions can produce shear-thinning flows which mix as well as Newtonian flows. Since significant effects are observed with less than a 4% difference in the velocity fields, the assumption of Newtonian kinematics can lead to large errors in the design and operation of process mixing equipment for non-Newtonian fluids.

• OSTI ID: 6658352
• Journal Information: AIChE Journal (American Institute of Chemical Engineers); (United States), Journal Name: AIChE Journal (American Institute of Chemical Engineers); (United States) Vol. 40:11; ISSN 0001-1541; ISSN AICEAC
• Country of Publication: United States
• Language: English

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